1. Field of the Invention
The invention relates to distributed processing systems. More particularly, the invention relates to distributed processing systems which incorporate a plurality of processing zones (referred to herein as xe2x80x9ccellsxe2x80x9d), each cell processing information in response to a type of event, and each cell communicating with other cells according to an event-reaction protocol as well as according to other protocols such as streaming, broadcast, etc. Cells exhibit a symmetrical and reciprocal relationship, with cells sometimes being a controller of other cells and sometimes being controlled by other cells. The system is self-configuring, self-repairing, and operates in real time.
2. State of the Art
The above referenced parent application disclosed a distributed processing system having a plurality of cells where each cell processes information in response to a type of event, and cells communicate with each other according to a variety of protocols including an (asynchronous) event-reaction protocol. Processing is truly distributed in that no cell is considered the system host or system controller. The cells exhibit a symmetrical and reciprocal relationship with cells sometimes being a controller of other cells and sometimes being controlled by other cells.
According to one embodiment, each cell is responsive to a single event and includes one or more scripts which are executed upon the occurrence of the event. At least some scripts include directions to send information to one or more scripts in another cell.
According to another embodiment, information exchanged between cells is categorized into the following types which are listed in descending order of priority: streams, data events, data event acks, spawn process, spawn process begun, spawn process ended, exception, and broadcast.
The cells may communicate with each other via a shared memory or via a communications bus. A scalable bandwidth bus is an ideal communications path. However, the communications protocol utilized by the cells enables the use of virtually any networking medium. Thus, cells may reside in the same chip or may be separated from each other by thousands of miles. A collection of interacting cells is referred to as a colony, regardless of where the cells are located, and a collection of cells which are closely located, e.g. on the same board, are referred to as a node. The modularity and scalability of the processing systems is therefore based on collections of cells and collections of colonies. Each cell may be embodied in hardware, software, or a combination of hardware and software. No cell or colony need be considered a xe2x80x9chostxe2x80x9d.
Each cell is provided with a collection of synchronous (non-colliding) scripts which respond to a single type of event. All scripts have addresses and the addresses of all of the scripts in the processing system are kept in a database by a resource manager script in each cell. Applications are created by linking available scripts via their respective addresses. As all scripts are driven by particular events, the code written for the distributed processing system does not require any explicit scheduling. The processing system is essentially self-scheduling and real time applications can run concurrently without interfering with each other.
Scripts communicate with each other by dynamically compiling and tearing down mailing lists which are based on the occurrence of specific events. Thus, in response to one specific event, a responding script will communicate with one set of other scripts; whereas in response to a different event, the responding script will communicate with a different set of other scripts. Scripts subscribe to and unsubscribe from the mailing lists of other scripts based on the occurrence of different events.
Cells advertise their presence in the network when connected, and periodically thereafter, in order that other cells be able to take advantage of their resources. In particular, each cell periodically (e.g. every second) updates its database of script addresses which represent the functionality of the system to accommodate the addition of new cells to the system and to accommodate for cells which have become disconnected from the system or which have stopped functioning for some reason. Thus, a processing system is readily expanded to include new and additional processing resources which are substantially automatically assimilated into the system. The processing system is, in this sense, self-configuring and self-repairing.
Communication among cells is effected with the aid of mailing lists such that data may be multicast from one cell to many cells. Moreover, the mailing lists are preferably dynamically set up and torn down depending on the execution of scripts which direct the flow of data throughout the system. Further, the mailing lists are updated as new cells are added to and old cells are removed from the system as part of the self-configuring and self-repairing functionality of the system.
An exemplary embodiment of a distributed processing system was illustrated with reference to a telephone private branch exchange PBX) in which cells are distributed over xe2x80x9cline cardsxe2x80x9d and xe2x80x9cphone cardsxe2x80x9d which couple several telephone sets to one or more telephone subscriber lines. In this example, the cells communicate with each other via the same physical medium through which the telephones are coupled to subscriber lines. Each line card and phone card is considered a node, each having a number of cells. Cells in the phone cards include, for example, cells responding to the following events: phone off hook, DTMF tone dialed, ring detected, etc. Examples of scripts executed in response to events include, generate dial tone, send ringing signal, seize subscriber line, etc. Each of the cards advertises its presence to the other cards on a regular basis. The knowledge of the presence of cards (nodes) in the system is used to build mailing lists when, for example, a conference call is made, or when the system is programmed so that only some phones in the system ring when an outside call is detected by a line card.
Subsequent development of the exemplary PBX system has led to the invention of several new features which can be used to provide the PBX with additional functionality and which can be used in any of the distributed processing systems according to the invention. Those skilled in the art will appreciate how these new features operate by comparing the source code of the Microfiche Appendix of this application with the source code of the Appendix of the previous application.
One of the important new features of the invention is that at least one cell is provided with the ability to read, write, and delete any address on any mailing list in the system.
Another new feature of the invention is that at least one cell keeps a list of events that are deemed important by the user where it is the cell""s responsibility to insure that it remains subscribed to the mailing lists associated with these events. For easy reference, this list is referred to as xe2x80x9cthe subscription listxe2x80x9d.
Yet another new feature of the invention is that at least one cell serves more than one mailing list and preferably keeps a list of the mailing lists it serves. This cell also has the ability to move subscribers from one mailing list to another, to modify which mailing list is the currently active mailing list or to make a plurality of mailing lists simultaneously active.
Still another important new feature of the invention is that at least one cell has the ability to modify the subscription list of another cell.
As described in more detail below with reference to the figures and the source code, these additional new features can be understood with regard to how they improve the functionality of the exemplary PBX system. For example, each phone card in the system will keep a subscription list (programmed by a human during system setup) of the line card mailing lists to which it is subscribed. This improves the self-healing and self-configuring aspects of the invention. In the PBX example of the prior application, each phone card attempted to subscribe to each line card and repeatedly attempted to join the mailing list of each line card. Most often, the line cards ignored the attempt to join as being redundant. In the case of a system failure, however, the repeated attempts to join line card mailing lists served a self-healing function. According to the new features of the invention, each phone card keeps a list of all of the line cards to which it has incoming access (the line card mailing lists to which it is subscribed) and a list of the line cards to which it has outgoing access. During periodic self-healing, the phone cards read the line card mailing lists to assure that they are still subscribed to the correct line cards. If they find that a line card mailing list which is indicated on their subscription list dose not list them as a subscriber, they re-subscribe to that list. When a phone goes off hook to make a call, the phone card runs down the list of line cards to which it has outgoing access until it finds a line card which is not in use. If all line cards are in use, the phone card will notify the user.
The feature of being able to read, write and delete any mailing list in the system coupled with the feature of being able to modify any subscription list in the system enable powerful self-configuring in which entirely new functionality can be automatically added to the system. For example, in the exemplary PBX system, a new call assistant card can be created which automatically intervenes between one or more line cards and one or more phone cards. The call assistant card can be configured to answer incoming calls and redirect them to particular phone cards in response to DTMF tones entered by the caller and can act as a phone directory and voicemail system. The call assistant card has the ability to read, write and delete the mailing lists on the line cards and also has the ability to read, write and delete the subscription lists of the phone cards. Thus, the call assistant card will, if directed to do so at the time it is added to the system, take a copy of the mailing lists of one or more line cards and substitute itself as the only subscriber to those line cards. It will also delete the appropriate line card addresses from one or more of the phone card incoming line subscription lists and substitute its address for the line card address. By doing this, the phone cards are automatically subscribed to the new call assistant and are automatically programmed to self-heal by re-subscribing to the call assistant rather than to the line cards.
The line cards are automatically reprogrammed to direct calls to the call assistant and the call assistant will automatically re-subscribe to the line cards when needed to self-heal.
The new feature of maintaining multiple mailing lists coupled with the feature of maintaining a list of the mailing lists enables new enhanced interworking among cells which was previously not readily enabled. For example, if a phone card is provided with two mailing lists for speech streams, call waiting is readily enabled. The first call or group of calls is placed on the first mailing list. A call waiting call or group of calls is placed on the second mailing list. Flashing the switch hook toggles from the first mailing list to the second mailing list. This effects a move from the first call or group of calls to the second call or group of calls. An option can be provided to make both mailing lists active at the same time and thereby merge the two groups. Multiple mailing lists in a phone card can enable many xe2x80x9cvoice channelsxe2x80x9d so that a number of calls or call groups can be handled simultaneously.
Additional objects and advantages of the invention will become apparent to those skilled in the art upon reference to the detailed description taken in conjunction with the provided figures.